83 



INSECTS INJURIOUS TO STAPLE CHOPS. 



soon killing it. Ordinarily, when feeding at night, the 

 worms are free from these parasites, bnt when the marcli- 

 ing habit is assumed these little flies swarm aroand them 

 on cloudy days, and before the next year will again have 

 the voracious army under subjection. Thus worms with 

 eggs upon them should never be destroyed if avoidable. 



Fig. 52. — The Farmer's Friend, the Red-tailed Tachina fly ( Win- 

 themiit 4-pustulat<i). a, natural size; b, much enhirged; c, army- 

 worm on which fly has laid eggs, natural size; d, same, much 

 enlarged. (After Slingerland.) 



Remedies. — When detected, all efforts should be centred 

 on keeping the worms out of crops not yet attacked and 

 confining their injury to one point. As a barrier, there 

 is nothing better than a steep ditch with the side next to 

 the crop to be protected as nearly vertical as possible. In 

 the bottom of this dig some deep holes every ten feet. 

 Not being able to easily scale the steep wall, the worms 

 will look for some easier ascent, and become accumulated 

 in large numbers in the holes, where they may be destroyed 



